We propose to investigate the relationship between indoor radon exposure and lung cancer using 350 non-smoking histologically confirmed lung cancer cases and 700 age/sex/smoking history matched controls selected by random-digit-dialing and HCFA payment rosters. The cases will be identified from new cases of lung cancer reported by the Utah and Idaho Cancer Registries. We propose to obtain a lifetime residential history and to measure indoor radon exposure for each case and control. Odds ratios will be calculated relating radon exposure to lung cancer and will be adjusted for confounding by passive smoking, exposure to other hazardous materials such as asbestos, and use of Vitamin A and it precursors.